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Allow specifying custom converters in Decoder
Add a new Decoder implementation, CustomDecoder, which allows users to specify custom type converters via its static factory method, create. To avoid duplicate code, introduce a new package private base class, AbstractRegistryDecoder, which the existing DefaultDecoder and CustomDecoder both extend. CustomDecoder will add the default factories used by DefaultDecoder as well, placing them after the custom ones so that they may be overridden and are only used as fallbacks.
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129
archaius2-core/src/main/java/com/netflix/archaius/AbstractRegistryDecoder.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,129 @@ | ||
| package com.netflix.archaius; | ||
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| import com.netflix.archaius.api.Decoder; | ||
| import com.netflix.archaius.api.TypeConverter; | ||
| import com.netflix.archaius.exceptions.ParseException; | ||
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|
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| import java.lang.reflect.Constructor; | ||
| import java.lang.reflect.Method; | ||
| import java.lang.reflect.Type; | ||
| import java.util.ArrayList; | ||
| import java.util.Collection; | ||
| import java.util.Collections; | ||
| import java.util.List; | ||
| import java.util.Map; | ||
| import java.util.Optional; | ||
| import java.util.concurrent.ConcurrentHashMap; | ||
| import java.util.stream.Stream; | ||
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| /** | ||
| * A {@code Decoder} implementation that also implements {@code TypeConverter.Registry}, and delegates to a supplied | ||
| * collection of converter factories. | ||
| */ | ||
| abstract class AbstractRegistryDecoder implements Decoder, TypeConverter.Registry { | ||
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| private final Map<Type, TypeConverter<?>> cache = new ConcurrentHashMap<>(); | ||
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| private final List<TypeConverter.Factory> factories; | ||
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| AbstractRegistryDecoder(Collection<? extends TypeConverter.Factory> factories) { | ||
| this.factories = Collections.unmodifiableList(new ArrayList<>(factories)); | ||
| } | ||
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| @Override | ||
| public <T> T decode(Class<T> type, String encoded) { | ||
| return decode((Type) type, encoded); | ||
| } | ||
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| @Override | ||
| public <T> T decode(Type type, String encoded) { | ||
| try { | ||
| if (encoded == null) { | ||
| return null; | ||
| } | ||
| @SuppressWarnings("unchecked") | ||
| TypeConverter<T> converter = (TypeConverter<T>) getOrCreateConverter(type); | ||
| if (converter == null) { | ||
| throw new RuntimeException("No converter found for type '" + type + "'"); | ||
| } | ||
| return converter.convert(encoded); | ||
| } catch (Exception e) { | ||
| throw new ParseException("Error decoding type `" + type.getTypeName() + "`", e); | ||
| } | ||
| } | ||
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| @Override | ||
| public Optional<TypeConverter<?>> get(Type type) { | ||
| return Optional.ofNullable(getOrCreateConverter(type)); | ||
| } | ||
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| private TypeConverter<?> getOrCreateConverter(Type type) { | ||
| TypeConverter<?> converter = cache.get(type); | ||
| if (converter == null) { | ||
| converter = resolve(type); | ||
| if (converter == null) { | ||
| return null; | ||
| } | ||
| TypeConverter<?> existing = cache.putIfAbsent(type, converter); | ||
| if (existing != null) { | ||
| converter = existing; | ||
| } | ||
| } | ||
| return converter; | ||
| } | ||
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| /** | ||
| * Iterate through all TypeConverter#Factory's and return the first TypeConverter that matches | ||
| * @param type | ||
| * @return | ||
| */ | ||
| private TypeConverter<?> resolve(Type type) { | ||
| return factories.stream() | ||
| .flatMap(factory -> factory.get(type, this).map(Stream::of).orElseGet(Stream::empty)) | ||
| .findFirst() | ||
| .orElseGet(() -> findValueOfTypeConverter(type)); | ||
| } | ||
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| /** | ||
| * @param type | ||
| * @param <T> | ||
| * @return Return a converter that uses reflection on either a static valueOf or ctor(String) to convert a string value to the | ||
| * type. Will return null if neither is found | ||
| */ | ||
| private static <T> TypeConverter<T> findValueOfTypeConverter(Type type) { | ||
| if (!(type instanceof Class)) { | ||
| return null; | ||
| } | ||
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| @SuppressWarnings("unchecked") | ||
| Class<T> cls = (Class<T>) type; | ||
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| // Next look a valueOf(String) static method | ||
| Method method; | ||
| try { | ||
| method = cls.getMethod("valueOf", String.class); | ||
| return value -> { | ||
| try { | ||
| return (T) method.invoke(null, value); | ||
| } catch (Exception e) { | ||
| throw new ParseException("Error converting value '" + value + "' to '" + type.getTypeName() + "'", e); | ||
| } | ||
| }; | ||
| } catch (NoSuchMethodException e1) { | ||
| // Next look for a T(String) constructor | ||
| Constructor<T> c; | ||
| try { | ||
| c = cls.getConstructor(String.class); | ||
| return value -> { | ||
| try { | ||
| return (T) c.newInstance(value); | ||
| } catch (Exception e) { | ||
| throw new ParseException("Error converting value", e); | ||
| } | ||
| }; | ||
| } catch (NoSuchMethodException e) { | ||
| return null; | ||
| } | ||
| } | ||
| } | ||
| } |
33 changes: 33 additions & 0 deletions
33
archaius2-core/src/main/java/com/netflix/archaius/CustomDecoder.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,33 @@ | ||
| package com.netflix.archaius; | ||
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| import com.netflix.archaius.api.TypeConverter; | ||
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| import java.util.ArrayList; | ||
| import java.util.Collection; | ||
| import java.util.List; | ||
| import java.util.Objects; | ||
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| /** | ||
| * A configurable {@code Decoder} implementation which allows extension through custom {@code TypeConverter.Factory} | ||
| * instances. The custom factories are searched first, and if no appropriate converter is found, the default | ||
| * converters used by {@code DefaultDecoder} will be consulted. | ||
| */ | ||
| public class CustomDecoder extends AbstractRegistryDecoder { | ||
| private CustomDecoder(Collection<? extends TypeConverter.Factory> typeConverterFactories) { | ||
| super(typeConverterFactories); | ||
| } | ||
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| /** | ||
| * Create a new {@code CustomDecoder} with the supplied {@code TypeConverter.Factory} instances installed. | ||
| * The default converter factories will still be registered, but will be installed AFTER any custom ones, | ||
| * giving callers the opportunity to override the behavior of the default converters. | ||
| * | ||
| * @param customTypeConverterFactories the collection of converter factories to use for this decoder | ||
| */ | ||
| public static CustomDecoder create(Collection<? extends TypeConverter.Factory> customTypeConverterFactories) { | ||
| Objects.requireNonNull(customTypeConverterFactories, "customTypeConverterFactories == null"); | ||
| List<TypeConverter.Factory> factories = new ArrayList<>(customTypeConverterFactories); | ||
| factories.addAll(DefaultDecoder.DEFAULT_FACTORIES); | ||
| return new CustomDecoder(factories); | ||
| } | ||
| } |
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33 changes: 33 additions & 0 deletions
33
archaius2-core/src/test/java/com/netflix/archaius/CustomDecoderTest.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,33 @@ | ||
| package com.netflix.archaius; | ||
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| import com.netflix.archaius.api.TypeConverter; | ||
| import org.junit.Assert; | ||
| import org.junit.Test; | ||
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| import java.lang.reflect.Type; | ||
| import java.util.Collections; | ||
| import java.util.Optional; | ||
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| public class CustomDecoderTest { | ||
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| @Test | ||
| public void testCustomTypeConverters() { | ||
| TypeConverter<String> stringConverter = String::toUpperCase; | ||
| TypeConverter<Long> longConverter = value -> Long.parseLong(value) * 2; | ||
| TypeConverter.Factory factory = (type, registry) -> { | ||
| if ((type instanceof Class<?> && ((Class<?>) type).isAssignableFrom(String.class))) { | ||
| return Optional.of(stringConverter); | ||
| } else if (type.equals(Long.class)) { // override default converter | ||
| return Optional.of(longConverter); | ||
| } | ||
| return Optional.empty(); | ||
| }; | ||
| CustomDecoder decoder = CustomDecoder.create(Collections.singletonList(factory)); | ||
| Assert.assertEquals("FOO", decoder.decode((Type) CharSequence.class, "foo")); | ||
| Assert.assertEquals("FOO", decoder.decode((Type) String.class, "foo")); | ||
| // default is overridden | ||
| Assert.assertEquals(Long.valueOf(6), decoder.decode((Type) Long.class, "3")); | ||
| // default converter is used | ||
| Assert.assertEquals(Integer.valueOf(3), decoder.decode((Type) Integer.class, "3")); | ||
| } | ||
| } |
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